What's the recommended approach when an Aggregate Root changes?

[Stijn Volders (ONE75)]

Hi,

Let's say I want to add a property to my "BacklogItem" class:

public Priority Priority {get;set;}

with a default value "Priority.High" (as always...)

When dealing with a RDMS, I would create the column with a default value and i'm ready to go. How do I update the documents in my database with RavenDB? I couldn't find info on the site about that, but maybe I'm looking with the wrong keywords (document change or migration yielded other results)

Thanks

Stijn

[Itamar Syn-Hershko]

You just add the property and set the default value in the object ctor, like you will normally do

It will just work from there.

[Stijn Volders (ONE75)]

thanks. That would work I guess.

Normally, I would add a parameter "priority" to the ctor and assign the value of the parameter to my property, so I don't need the "default" value in my code. Only the current documents in the database violate my invariant.

I just did some tests. Apparently the values of my ctor parameters are defaulted when the document is deserialized. I've tried it with an enum and the first value of my enum was used if there is nothing in my document (not a null value, the property itself is also not in the document)

that's kind of tricky behavior, no?

[Matt Warren]

Well if the field doesn't exist in the doc/json, there's no value for RavenDB to deserialize, so it's just left as the default/existing value.

Have a read of this blog post, it give you so more info about doing migrations.

[Matt Warren]

If you want to change the actual data in the doc store, rather than what is deserialised, you can use patching

See http://ravendb.net/docs/client-api/set-based-operations and http://ravendb.net/docs/client-api/partial-document-updates

On Monday, 23 April 2012 23:15:45 UTC+1, Stijn Volders (ONE75) wrote:

[Stijn Volders (ONE75)]

Thanks Matt! Looks like everything I need to know is in these posts.

[Ryan Heath]

What you see here, is that c'tors are not invoked during deserializing.
Your enum property was just initialized with value 0, which is the
value or your first enum value.

// Ryan

On Tue, Apr 24, 2012 at 12:15 AM, Stijn Volders (ONE75)

[Oren Eini (Ayende Rahien)]

Actually, the ctor IS invoked

[Ryan Heath]

Do you (Raven) call it yourself? The .net infrastructure does not.

// Ryan

[Oren Eini (Ayende Rahien)]

Yes, it does.

Unless you call UnsafeCreateObject ( or something like that)

[Matt Warren]

I ran into this the other week, if you use the code below, it won't call the ctor (I think WCF deserialization uses this)

   FormatterServices.GetUninitializedObject(typeof(MyClass)) 

See http://stackoverflow.com/a/390596/4500 for more info.

[Ryan Heath]

Hmm,

This test fails:

[Serializable]
public class Class1
{
[NonSerialized]
public int nonSerialized;

public Class1()
{
nonSerialized = 42;
}
}

[TestFixture]
public class Test
{
[Test]
public void TestCtor()
{
var myObject = new Class1();
var formatter = new BinaryFormatter();

var mem = new MemoryStream();
formatter.Serialize(mem, myObject);
mem.Position = 0;
var newObject = (Class1)formatter.Deserialize(mem);

Assert.That(newObject.nonSerialized, Is.EqualTo(42));
}
}

Which serialization do you use?

// Ryan

On Tue, Apr 24, 2012 at 11:34 AM, Oren Eini (Ayende Rahien)

[Oren Eini (Ayende Rahien)]

That is because you are using binary serialization. Json serialization and just about anything else calls the ctor.

[Ryan Heath]

Ah, learning something new each day :)
I was pretty sure serialization was not calling the ctor, but I did
not think about the other serialization types.

It feels troublesome they don't behave alike ...

// Ryan

On Tue, Apr 24, 2012 at 11:54 AM, Oren Eini (Ayende Rahien)

[Matt Warren]

It is wierd, but I wonder if the expectation around binary serialisation is different, i.e. you wouldn't expect it to call the ctor because it's in effect making a binary clone of your object?

The others are more explicit, from what I remember the XMLSerializer demands that you have a public parameterless ctor, so there's an expectation that it will call it.